JP5935540B2 - High density liquid discharge head and image forming apparatus - Google Patents

Description

  The present invention relates to a high-density liquid discharge head and an image forming apparatus used for a printer, a copying machine, a facsimile machine, and the like.

  In various image forming apparatuses such as printers, facsimiles, copiers, plotters, printer / facsimile / copier multifunction machines, etc., a liquid ejecting apparatus that mounts a liquid ejecting head for ejecting a recording liquid and forms an image on a recording medium is provided. What you have is known. The liquid discharge device is also called a recording medium (recording medium, transfer paper, paper, etc.) such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc., regardless of the material. Is used as a synonym.) Means a device for ejecting liquid, and “recording” not only applies an image having a meaning such as a character or a figure to a recording medium, but also a pattern. It also means that an image having no meaning such as is given to a recording medium, and image formation, printing, printing, and printing are also used synonymously.

  For example, as an ink jet head as a liquid discharge head, a head in which a piezoelectric body is laminated or formed in a thin film shape as a pressure generating means for generating pressure to pressurize ink that is liquid in a liquid chamber, a head having a heating element, etc. It has been known.

  In this ink jet head, if the viscosity of the ink changes due to a change in the environmental temperature to be used, there may be a case where sufficient ejection cannot be performed.

  In such a case, ink ejection is not performed with high accuracy, and image quality is degraded.

  In particular, when an inkjet printer is used in a low temperature environment such as early morning in winter, there is a case where sufficient ink ejection cannot be performed for a while after the start of use.

  Because of such problems, Patent Document 1 (Japanese Patent Laid-Open No. 2005-254463) proposes providing a heating means such as a heater in the vicinity of the head of an ink jet printer.

  However, if a new heating means is provided in this way, the number of parts in the vicinity of the head increases and the configuration becomes complicated. Further, it is difficult to control the heating of the ink in the liquid storage chamber of the head over a wide range, and it is extremely difficult to maintain the head temperature even when the above-described heating control using the heater is used. difficult.

  As means for solving these problems, in Patent Document 2 (Japanese Patent Laid-Open No. 11-138798), a heating signal is applied to the piezo element under the condition that ink is not discharged, thereby heating the piezo element using heat generated. It has been proposed to perform delicate temperature adjustment by installing a temperature detection means. Since no new heating means is provided, the configuration can be simplified and the temperature can be controlled.

  However, in the actual use environment, not only the viscosity change due to the use environment temperature, but also the ink surface (hereinafter referred to as meniscus) dries at the nozzle portion that has not been ejected for a predetermined period of time, resulting in a local increase in viscosity. Will occur. When this local increase in viscosity occurs, a maintenance operation such as empty ejection is performed outside the non-printing area. Conventionally, even if idle ejection is performed, there are many cases in which ejection characteristics are defective, and it is necessary to restore by performing operations such as ink suction from the nozzle surface, resulting in an extremely large amount of ink disposal. Therefore, it is desirable that the recovery can be performed by the idle discharge operation.

  Here, in particular, an inkjet head using a thin-film piezoelectric element as an actuator increases the viscosity slightly in the low temperature range due to the small deformation force of the actuator, and when the meniscus drying increases, a heating signal is applied to slightly increase the temperature. Even if the idle ejection operation is performed, it may not be possible to return to normal ejection, and it is necessary to perform a maintenance operation by the ink suction operation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a high-density liquid discharge head and an image forming apparatus that can be refreshed by idle discharge and normally discharged early in order to reduce the frequency of maintenance due to an ink suction operation or the like.

In order to achieve this object, the present invention comprises an actuator substrate provided with a plurality of liquid chambers,
A plurality of nozzles for discharging ink from the plurality of liquid chambers;
A thin-film diaphragm that closes an upper portion of the liquid chamber; and a thin-film piezoelectric element provided on the diaphragm; and the diaphragm is vibrated by the piezoelectric element, whereby the liquid chamber A thin film actuator that pressurizes the ink, a driving IC that is provided on the actuator substrate and that drives and controls the piezoelectric element, and a head temperature detection element that detects the temperature in the liquid chamber, The driving IC controls the driving of the piezoelectric element based on the detected temperature signal from the head temperature detecting element, so that the piezoelectric element and the driving IC generate heat during the driving control of the piezoelectric element, respectively. A high-density liquid ejection head capable of raising the ink temperature in a room, wherein the drive control is performed under a condition that ink is not ejected from the nozzles before printing is started. Applying a dynamic voltage waveform to the piezoelectric element causes the piezoelectric element to generate heat, and simultaneously generates heat, thereby preheating the liquid chamber to a temperature higher than a predetermined temperature in the liquid chamber, and the liquid An empty discharge step of discharging the ink in the liquid chamber from the nozzle until the liquid in the chamber reaches an appropriate temperature for printing; and from the nozzle when the liquid in the liquid chamber reaches an appropriate temperature for printing. And a printing step of starting a printing operation by discharging a liquid. The image forming apparatus according to the present invention is equipped with the high-density liquid discharge head.

  According to this configuration, since the maintenance frequency due to the ink suction operation or the like is reduced, refreshing can be performed by idle ejection and normal ejection can be performed early.

It is sectional drawing of the Example which applied the high-density liquid discharge head which concerns on this invention to the inkjet head of 2 rows of nozzle rows. It is a top view of the inkjet head which abbreviate | omitted the flame | frame, diaphragm, and FPC of FIG. It is a top view of the inkjet head which abbreviate | omitted the upper frame of FIG. It is sectional drawing which follows the A1-A1 line | wire of FIG. It is sectional drawing which follows the A2-A2 line | wire of FIG. It is sectional drawing which follows the A3-A3 line | wire of FIG. It is a top view of the inkjet head which abbreviate | omitted the flame | frame of FIG. It is explanatory drawing which shows the maintenance operation | movement control of the nozzle part (nozzle) before the printing start. It is sectional drawing which shows the other example of the high-density liquid discharge head of this invention. It is a schematic explanatory drawing of the image forming apparatus of Example 3 to which the high-density liquid discharge head (inkjet head) concerning this invention is applied. FIG. 10 is a schematic plan view showing the relationship between the high-density liquid ejection head (inkjet head) of FIG. 9 and the operation direction. 10 is a circuit diagram showing the relationship between the head controller and the temperature detection element. 12 is a flowchart of print control by the head controller of FIG. 11.

A first embodiment of a high-density liquid ejection head according to the present invention will be described below with reference to FIGS.
[Constitution]
A. Basic Configuration FIG. 1 is a cross-sectional view of an embodiment in which the high-density liquid discharge head according to the present invention is applied to an inkjet head having two nozzle rows. FIG. 2 is a plan view of the ink jet head in which the frame, the diaphragm, and the FPC in FIG. 1 are omitted. FIG. 2A is a plan view of the inkjet head from which the upper frame of FIG. 1 is omitted. 3 is a cross-sectional view taken along line A1-A1 in FIG. 1, FIG. 4 is a cross-sectional view taken along line A2-A2 in FIG. 1, and FIG. 5 is a cross-sectional view taken along line A3-A3 in FIG. FIG. 6 is a plan view of the ink jet head in which the frame of FIG. 1 is omitted.

  Although the configuration of the first embodiment is described as an example applied to an inkjet head having two nozzle rows, the present invention can be similarly applied to an inkjet head having more than two nozzle rows.

  In FIG. 1, reference numeral 1 denotes an actuator substrate made of a laminated body of glass or a thin metal plate, a silicon substrate, or the like. The actuator substrate 1 is preferably made of a silicon substrate. When the actuator substrate 1 is made of a silicon substrate or the like, the plurality of liquid chambers 2 can be formed by etching the silicon substrate.

  As shown in FIG. 1, a plurality of liquid chambers (individual liquid chambers) 2 opened on both surfaces (the upper surface and the lower surface of the actuator substrate 1 in FIG. 1) are formed on the actuator substrate 1. As shown in FIG. 2, each of the liquid chambers 2 is elongated in a straight line in the short direction of the actuator substrate 1 (left and right direction in FIG. 2).

  As shown in FIGS. 2 and 3, the plurality of liquid chambers 2 are first liquids arranged in a straight line at an equal pitch in the longitudinal direction of the actuator substrate 1 (vertical direction in FIG. 2, horizontal direction in FIG. 3). 2 and 4, as shown in FIGS. 2 and 4, the second liquid chamber row Lq2 arranged linearly at an equal pitch in the longitudinal direction of the actuator substrate 1 (vertical direction in FIG. 2, horizontal direction in FIG. 4). Is configured. In addition, the first and second liquid chamber rows Lq1 and Lq2 are arranged in two rows (parallelly arranged in the short direction) toward the short side direction (left and right direction in FIG. 2) of the actuator substrate 1. Here, the side edges in the short direction of the actuator substrate 1 are denoted by 1a and 1b as shown in FIGS.

  A plurality of individual flow paths 3 corresponding to the liquid chambers 2 of the first and second liquid chamber rows Lq1 and Lq2 and opened on both surfaces of the actuator substrate 1 are provided on the side edge portions 1a and 1b of the actuator substrate 1, respectively. Are formed respectively. The side edges 1a and 1b are formed with a plurality of notch-shaped individual communication passages 4 that open to one surface side of the actuator substrate 1 and communicate with the individual flow paths 3 and the liquid chambers 2, respectively. .

  The individual communication passage 4 on the first liquid chamber row Lq1 side and the individual communication passage 4 on the second liquid chamber row Lq2 side are the elongated liquid chamber 2 in the first liquid chamber row Lq1 and the elongated liquid in the second liquid chamber row Lq2. The chambers 2 communicate with portions of the chamber 2 opposite to each other.

The individual communication path 4 is formed in a small cross-sectional area, and restricts the flow rate of the liquid flowing from the individual flow path 3 to the liquid chamber 2. When the actuator substrate 1 is made of a silicon substrate or the like, the liquid chamber 2, the individual flow path 3, the individual communication path 4 and the like can be formed by etching.
(Nozzle plate 5, nozzle 6)
As shown in FIG. 1, each liquid chamber 2, the individual flow path 3, and the individual communication path 4 are joined to one surface of the actuator substrate 1 at the open end to the one surface side (the lower surface in FIG. 1) ( It is closed by the nozzle plate 5 that is fixed.

  The nozzle plate 5 is formed of a resin or a metal material. As shown in FIGS. 1, 3, and 4, the nozzle plate 5 is formed with a plurality of nozzles 6 communicating with the liquid chambers 2 as nozzle portions. Has been. As shown in FIG. 2, the plurality of nozzles 6 are arranged in two rows in the short direction (left and right direction in FIG. 2) of the actuator substrate 1, and two rows 6 arranged in parallel in the short direction. The first and second nozzle rows Nz1, Nz2 are configured (formed).

The nozzle 6 of the first nozzle row Nz1 and the nozzle 6 of the second nozzle row Nz2 are positioned adjacent to the first liquid chamber row Lq1 and the second liquid chamber row Lq2, as shown in FIGS. It has been. That is, the nozzle 6 of the first nozzle row Nz1 and the nozzle 6 of the second nozzle row Nz2 are the end portions of the liquid chamber 2 of the first liquid chamber row Lq1 and the liquid chamber 2 of the second liquid chamber row Lq2 on the adjacent sides. Communicating with
(Vibration plate 7)
In the present embodiment, the other surface side end portion of the actuator substrate 1 of the liquid chamber 2 is closed by a thin film diaphragm 7 provided on the other surface of the actuator substrate 1. The diaphragm 7 is formed from a SiO ₂ layer of an SOI (Silicon On Insurator) substrate. Further, when the actuator substrate 1 is formed of a support substrate of a laminated body of glass or a thin metal plate as described above, the actuator substrate 1 and a separate SOI substrate are bonded or bonded to the actuator substrate 1 and bonded together. By polishing this SOI substrate into a thin film, the thin film SOI substrate can be used as the diaphragm 7.

  In addition, even when the actuator substrate 1 is made of a silicon substrate or the like as described above, an SOI substrate separate from the actuator substrate 1 is bonded or bonded to the actuator substrate 1 and bonded together, and the SOI substrate is thin-film-shaped. The thin film SOI substrate can be used as the diaphragm 7 by polishing the substrate.

If the actuator substrate 1 is made of a silicon substrate or the like as described above, a portion of the silicon substrate where the SiO ₂ layer is not formed is formed by forming a thin-film SiO ₂ layer on one surface of the silicon substrate. An actuator substrate body (support substrate) can also be used. This actuator substrate body is the actuator substrate 1 in FIG.

When the silicon substrate is etched from the other side to form a plurality of liquid chambers 2, the SiO ₂ layer can be used as an etching stop layer. By forming the liquid chamber 2, a thin SiO ₂ layer can be formed on one surface of the silicon substrate as the diaphragm 7 in FIG. By making the diaphragm 7 into a thin film diaphragm formed of Si _N (SiO ₂ ) or the like in this way, the cost is lower than that of the SOI substrate, so that the cost can be reduced. When the actuator substrate 1 is formed from a silicon substrate, the diaphragm 7 can be formed integrally with the actuator substrate 1.

As shown in FIG. 1, the diaphragm 7 is formed with a communication path 7 p corresponding to the individual flow path 3 and corresponding to the individual flow path 3.
(Piezoelectric element 8, wiring)
As shown in FIG. 1, a thin film PZT [that is, Pb (ZrTi) formed on the surface of the diaphragm 7 opposite to the liquid chamber 2 by a processing method such as sputtering or a sol-gel method. O ₃ ] is provided as a thin film piezoelectric element (thin film piezoelectric element) 8. However, although the thin film piezoelectric element (thin film piezoelectric element) 8 is formed from the thin film PZT here, the piezoelectric element 8 may be a piezoelectric element other than PZT.

  The piezoelectric element 8 expands and contracts when an AC voltage is applied to vibrate the vibration plate 7, and the vibration plate 7 applies pressure to the liquid chamber 2. Thus, the piezoelectric element 8 constitutes an actuator together with the vibration plate 7. ing. Further, as shown in FIGS. 5 and 6, the plurality of piezoelectric elements 8 are linearly arranged in two rows, and constitute (form) two rows of first and second piezoelectric element rows Pz1 and Pz2. doing. Here, in FIG. 6, 7 a and 7 b are side edges of the diaphragm 7 opposite to each other in the juxtaposition direction of the first and second piezoelectric element arrays Pz 1 and Pz 2, and 7 c is the first and second piezoelectric elements of the diaphragm 7. It is an end in the extending direction of the element rows Pz1, Pz2.

  As shown in FIG. 6, on the surface of the diaphragm 7 opposite to the liquid chamber 2, a first Com wiring (that is, a first Com pattern wiring) 9 extending along the side edge portion 7a and the end portion 7c, A second Com wiring (that is, a second Com pattern wiring) 10 extending along the edge 7b and the end 7c is formed by etching or the like. Each piezoelectric element 8 of the first piezoelectric element array Pz1 is connected to the first Com wiring 9, and each piezoelectric element 8 of the second piezoelectric element array Pz2 is connected to the second Com wiring 10.

  Further, an input terminal 9 a branched from the first Com wiring 9 and an input terminal 10 a branched from the second Com wiring 10 are formed at the end 7 c of the diaphragm 7. Further, Vcom wirings 11 and 12 are formed at the end 7c of the diaphragm 7 between the first Com wiring 9 and the second Com wiring 10, and a plurality of inputs branch from the Vcom wirings 11 and 12. Terminals 11a and 12a are formed. A plurality of input terminals 13 positioned between the input terminals 11 a and 12 a are formed at the end 7 c of the diaphragm 7.

The plurality of liquid chambers 2, nozzles 6 and piezoelectric elements (thin film-like piezoelectric elements) 8 correspond to those shown in FIG. 1, FIG. 3 and FIG. ). A plurality of liquid discharge head portions are provided corresponding to each liquid chamber 2 and are arranged in two lines in a straight line, and two rows of first and second liquid discharge head portion rows (reference numerals omitted). ) Is formed (formed).
(Lower frame plate 14)
As shown in FIGS. 1, 3, and 4, a lower frame plate (subframe) 14 is joined (fixed) on the diaphragm 7. The lower frame plate 14 is formed with a plurality of vibration allowing recesses 14a facing the piezoelectric elements 8 of the first and second piezoelectric element rows Pz1 and Pz2. The plurality of vibration allowing recesses 14 a are linear and have the same shape as the elongated liquid chamber 2, and are provided so as to coincide with the respective liquid chambers 2.

  As shown in FIGS. 1 and 2A, the lower frame plate 14 is provided with an arrangement space 14b that is located between the first and second piezoelectric element rows Pz1 and Pz2 and that opens on the upper and lower surfaces. In 14b, a driving IC 15 fixed on the diaphragm 7 is disposed as a control device (control unit, control circuit). The driving IC 15 is sealed with an underfill agent 15a, and the back surface side is not in contact with other components.

The drive IC 15 is wired to one end of each piezoelectric element 8 and is wired to the input terminals 11a, 12a, and 13 so as to drive and control the piezoelectric element 8 on the diaphragm 7.
(Upper frame plate 16)
Further, as shown in FIG. 1, an upper frame plate (upper frame) 16 is bonded (fixed) on the lower frame plate 14. As shown in FIG. 1, the lower frame plate 14 and the upper frame plate 16 are formed on the opposite side edge portions so as to straddle the lower frame plate 14 and the upper frame plate 16, and the first and second piezoelectric elements. First and second common liquid chambers 17a and 17b are formed on the opposite sides of the element rows Pz1 and Pz2, respectively. The first and second common liquid chambers 17a and 17b extend along the arrangement direction of the individual flow paths 3 as shown in FIG. 2A. Further, as shown in FIG. 1, the portions corresponding to the first and second piezoelectric element rows Pz1 and Pz2 of the upper frame plate 16 are respectively connected to the first and second common liquid chambers 17a and 17b. Mouth 16a, 16b is formed. The supply ports 16a and 16b are provided in the upper frame plate 16 so as to be positioned at substantially the center or the end side in the extending direction of the first and second piezoelectric element rows Pz1 and Pz2, for example.
(Bonding club)
The nozzle plate 5 is formed such that the dimension in the extending direction of each of the first and second nozzle arrays Nz1 and Nz2 (that is, the arrangement direction of the nozzles 6 in the first and second nozzle arrays Nz1 and Nz2) is larger than the dimension of the actuator substrate 1. Has been. As a result, the extending portions 5a projecting from the end of the actuator substrate 1 are provided on both ends of the nozzle plate 5 in the extending direction of the first and second nozzle rows Nz1 and Nz2, as shown in FIGS. (The other not shown) is formed as a protruding end.

  On the extended portion 5a, a wiring end 18a of a FPC (flexible wiring board) 18 for wiring connection is disposed. A plurality of wiring terminals 19 are arranged in parallel on the surface of the wiring end 18a. Further, as shown in FIGS. 3 and 4, a backing plate 20 is fixed to the back surface of the wiring end portion 18a. By fixing the backing plate 20 to the extended portion 5a, the wiring end 18a of the FPC 18 is attached on the extended portion 5a.

The plurality of wiring terminals 19 of the wiring end portion 18a are bonded to the plurality of input terminals 11a, 12a, and 13 provided on the diaphragm 7 by bonding wires 21 (wire bonding).
(Temperature detection element)
The high-density liquid discharge head is provided with a temperature detection element (head temperature detection element) 22 such as a thermistor for detecting the ink temperature in the liquid chamber (individual liquid chamber) 2 as shown in FIGS. 2A and 5. . The temperature detecting element 22 is desired to detect the ink temperature in the liquid chamber (individual liquid chamber) 2 with high accuracy. For this reason, the temperature detection element 22 is provided on the nozzle plate 5, the actuator substrate 1, or the vibration plate 7 of the actuator substrate 1 adjacent to the liquid chamber (individual liquid chamber) 2.

In this embodiment, the temperature detection element 22 is provided on the upper surface of the diaphragm 7 adjacent to the driving IC 15. The temperature detection signal from the temperature detection element 22 is input to the driving IC 15.
[Action]
Next, other configuration conditions and operations of the inkjet head which is the high-density liquid ejection head having such a configuration will be described.
(i). Maintenance operation control of the nozzle part (nozzle) before the start of printing (empty ink ejection control of the meniscus part in the nozzle part (nozzle 6) before printing)
As described above, the plurality of nozzles 6 for discharging the liquid, the liquid chamber 2 with which the nozzle 6 communicates, and the actuator (the vibration plate 7 and the piezoelectric element for generating pressure to pressurize the liquid in the liquid chamber 2) 8) In the high-density liquid ejection head having the temperature detection element 22, the actuator (the vibration plate 7 and the piezoelectric element 8) is formed on the actuator substrate 1 in a thin film shape. A driving IC 15 is mounted on the actuator substrate 1. When the piezoelectric element 8 is driven, the piezoelectric element 8 and the driving IC 15 generate heat. Therefore, the piezoelectric element 8 and the driving IC 15 are configured to have a high heat generation density and to allow the actuator to easily transmit heat to the ink in the liquid chamber 2 through the substrate 1.

  However, since heat is exhausted by the ejected ink during normal printing, an increase in the temperature of the head can be suppressed.

  In particular, in the nozzle portion (nozzle 6) that is not discharged for a certain period of time in a low temperature and low humidity environment, local drying is likely to occur in the meniscus portion, and the viscosity of the ink increases in a low temperature environment. The piezoelectric element 8 cannot secure a large amount of displacement. For this reason, even if the resonance drive waveform of the liquid chamber 2 (individual liquid chamber) is used as the drive waveform (vibration waveform) of the piezoelectric element 8, it is difficult to perform idle discharge (normal maintenance operation). The meniscus portion refers to a portion where the tip of the ink in the nozzle 6 is dented or raised in a convex shape due to surface tension or the like.

  Here, as the preheating before the idle discharge of the nozzle portion (nozzle 6), the drive voltage waveform is applied from the driving IC 15 to the piezoelectric element 8 under the condition that the ink is not discharged, so that exhaust heat due to the ink does not occur. The ink temperature in the liquid chamber 2 (individual liquid chamber) rises.

  That is, when driving power for printing is supplied to the driving IC 15 from a control circuit (not shown) via the FPC 18, the driving IC 15 applies a voltage to the piezoelectric element 8 to cause the piezoelectric element 8 to generate heat and generate self-heating. Start. At this time, a temperature detection signal is input from the temperature detection element 22 to the driving IC 15.

  In this state, as shown in FIG. 7, the driving IC 15 performs a preliminary operation higher than the printing temperature (printing start temperature X2) set from the environmental temperature X1 at time t1 before the nozzle portion (nozzle 6) is idlely discharged. The ink temperature in the liquid chamber 2 (individual liquid chamber) is raised until time t2 when the heating temperature becomes X3. When the driving IC 15 detects from the temperature detection signal from the temperature detection element 22 that the ink temperature in the liquid chamber 2 (individual liquid chamber) has reached the preheating temperature X3, the driving IC 15 vibrates (actuates) the piezoelectric element 8. In this way, the nozzle portion (nozzle 6) is ejected idle. Thereby, ink is ejected from the nozzle part (nozzle 6), the heat in the liquid chamber 2 (individual liquid chamber) is wasted together with the ink, and the temperature in the liquid chamber 2 is lowered. When the temperature in the liquid chamber 2 reaches the printing temperature (printing start temperature X2) at time t3, the driving IC 15 starts printing.

  By performing the ink ejection operation in this manner, the ink viscosity at the nozzle portion (nozzle 6) is reduced, and vibration of the dried meniscus portion of the nozzle portion (nozzle 6) can also be obtained. Become.

  The ink temperature in the liquid chamber 2 (individual liquid chamber) is lowered by the exhaust heat due to the idle discharge. As a feature here, although the heat generation density of this head configuration is high, since the heat capacity of each nozzle part (nozzle 6) is small, the temperature is suddenly lowered by the heat exhausted from the nozzle part (nozzle 6). The object is to quickly reduce the viscosity of the ink in the meniscus portion and quickly reach the printing temperature (printing start temperature X2).

  As described above, since the temperature of the liquid chamber 2 (individual liquid chamber) quickly returns to a predetermined temperature or less, the start time until the printing operation can be shortened during the maintenance operation.

  As the idle discharge waveform, the meniscus vibration can be increased by matching with the resonance period of the liquid chamber 2 (individual liquid chamber), and the idle discharge can be stably performed.

  Since the driving IC 15 is mounted on the actuator substrate 1 between the two nozzle rows as in this configuration, the heat generated by the driving IC 15 can be transmitted uniformly in the nozzle row direction. The ink in the liquid chamber 2 (individual liquid chamber) can be efficiently heated during the preliminary heating.

  The driving IC 15 is flip-chip mounted on the actuator substrate 1 and sealed with the underfill agent 15a shown in FIG. The back surface side of the driving IC 15 is in a hollow state without contacting other parts.

For this reason, the heat generated in the driving IC 15 is efficiently transmitted to the actuator substrate 1, and waste heat by ink is efficiently performed during printing, and the liquid chamber 2 (individual liquid chamber) is efficiently performed during preheating. It has the effect of increasing the ink temperature inside.
(ii) Control of drive voltage waveform cycle of piezoelectric element 8 by drive IC 15, that is, drive waveform (vibration waveform) of piezoelectric element 8 The drive waveform (vibration waveform) of piezoelectric element 8 in the above configuration will be described.

Since the driving IC 15 is mounted between the two nozzle rows, the connection terminal of the FPC 18 is pulled out in the short direction of the head. That is, as shown in FIG. 2A, the current that flows during charging / discharging of the piezoelectric element 8 is concentrated in the first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12, and current corresponding to the drive channel (nozzle) flows. Here, when all channels (nozzles) such as preheating and idle discharge are continuously driven, the first and second Com wirings 9 and 10 and the Vcom wiring 11 on the actuator substrate 1 are charged and discharged to the piezoelectric element 8. , 12 becomes very large. For this reason, in order to solve problems such as electromigration, the cross-sectional area of the wiring is increased. In this case, a design change such as increasing the wiring thickness or increasing the wiring width is required, resulting in an increase in the cost of the head configuration.

  For this reason, in order to reduce the electric current of the wiring part at the time of preheating or empty discharge, the following measures are good.

  By making the drive voltage waveform period, that is, the drive waveform (vibration waveform) of the piezoelectric element 8 by the drive IC 15 during the preheating longer than the resonance period of the liquid chamber 2 (individual liquid chamber), the first and second Com wires 9, 10, the effective current of the current flowing through the Vcom wirings 11 and 12 is reduced.

  Here, each nozzle 6 or each liquid chamber 2 (individual liquid chamber) communicating with each nozzle 6 or a liquid passage (ink passage) formed across the nozzle 6 and the liquid chamber 2 is a single channel. The drive control of the piezoelectric element 8 corresponding to each channel by the IC 15 is performed as follows.

  In the following description, each liquid chamber 2 is described as one channel, the piezoelectric element 8 corresponding to each liquid chamber 2 is driven by the driving IC 15, and each liquid chamber 2 is heated by the heat generated by each piezoelectric element 8. In this case, the liquid chamber 2 heated by the piezoelectric element 8 will be described as a drive channel.

  The drive channel heated by the piezoelectric element 8 driven by the driving IC 15 at the time of preheating is divided into, for example, every other channel, and the piezoelectric elements 8 of the divided channels are driven, whereby the first and second Com wirings 9 , 10, while limiting the current flowing in the Vcom wirings 11 and 12 simultaneously, the piezoelectric elements 8 of all the channels are driven with a time difference by switching the switching of the piezoelectric elements 8 of the divided channels at high speed. All the channels (nozzle 6 and liquid chamber 2) are preheated.

  As described above, the plurality of channels are divided and the drive waveform (drive voltage waveform cycle) of the piezoelectric element 8 of each channel that is divided and driven is made faster than the resonance cycle of the liquid chamber 2, thereby The heat generation of the element 8 can be increased to increase the heat generation efficiency, and the current flowing through the wiring portion can be limited.

By setting the rise and fall times of the drive waveform during preheating longer than the drive waveform during ink ejection, the maximum current and effective current flowing through the wiring section can be reduced. For example, by dividing every other channel (one nozzle 6) and driving the piezoelectric elements 8 of the divided channels, the current flowing simultaneously to the plurality of piezoelectric elements 8 is limited, while the plurality of piezoelectric elements 8 are operated at high speed. Thus, the exhaust heat in the plurality of liquid chambers 2 can be rapidly made by switching and switching.

  FIG. 8 shows another embodiment of the present invention. The basic configuration of the high-density liquid ejection head of this embodiment is the same as that of the first embodiment. In this embodiment, the supply port 16a (16b) is formed near the center of the nozzle row. Since the ink is transmitted in the vicinity of the supply port 16a (16b), the temperature of the individual liquid chamber in the vicinity of the supply port 16a (16b) is less likely to rise than both ends.

  For this reason, the channel in the vicinity of the supply port 16a (16b) is controlled so that the power consumption by the preheating increases.

  9 and 10 show the third embodiment. The third embodiment shows an example in which the high-density liquid discharge head of the first embodiment is applied to an image forming apparatus such as a printer. The basic configuration of the high-density liquid ejection head of Example 3 is the same as that of Example 1.

  9 and 10, the image forming apparatus holds the carriage 103 slidably in the main scanning direction by a guide rod 101 and a guide rail 102, which are guide members horizontally mounted on left and right side plates (not shown). The motor 104 moves and scans in the direction indicated by the arrow (main scanning direction) via the timing belt 105 spanned between the driving pulley 106A and the driven pulley 106B.

  For example, a recording head 107 for forming a color image is held on the carriage 103. The recording head 107 includes a high-density liquid ejection head 107k that ejects droplets (ink droplets) of black (K) recording liquid (ink), and a color droplet of cyan (C) color recording liquid (ink). High-density liquid ejection head 107c that ejects (ink droplets), high-density liquid ejection head 107m that ejects droplets (ink droplets) of magenta (M) color recording liquid (ink), and yellow (Y) color A high-density liquid ejection head 107y that ejects droplets (ink droplets) of recording liquid (ink) is provided. The high-density liquid discharge heads 107k, 107c, 107m, and 107y use the configuration of the high-density liquid discharge head of Example 1 or Example 2.

  Further, the high-density liquid ejection heads 107k, 107c, 107m, and 107y are arranged in a direction along the main scanning direction, and are mounted with the droplet ejection direction facing downward. In addition, although the independent high-density liquid discharge head is used here, it is also possible to employ a configuration in which one or a plurality of heads having a plurality of nozzle rows that discharge the recording liquid droplets of each color are used. Further, the number of colors and the arrangement order are not limited to this.

  The carriage 103 is equipped with a sub tank 108 for each color for supplying each color ink to the recording head 107. Ink is supplied to the sub tank 108 from a main tank (ink cartridge) (not shown) via an ink supply tube 109.

  On the other hand, as a sheet feeding unit for feeding a recording medium (sheet) 112 loaded on a sheet stacking unit (pressure plate) 111 such as a sheet feeding cassette 110, the sheets 112 are separated and fed from the sheet stacking unit 111 one by one. Opposite to the half-moon roller (feed roller) 113 and the feed roller 113 to be fed, a separation pad 114 made of a material having a large friction coefficient is provided, and this separation pad 114 is urged toward the feed roller 113 side.

  As a transport unit for transporting the paper 112 fed from the paper feed unit below the recording head 107, a transport belt 121 for electrostatically attracting and transporting the paper 112, and a paper feed unit A counter roller 122 for transporting the paper 112 fed through the guide 115 while sandwiching it between the transport belt 121 and the paper 112 fed substantially vertically upward is changed by about 90 ° and copied on the transport belt 121. And a pressure roller 125 </ b> A and a tip pressure roller 125 </ b> B urged toward the conveyance belt 121 by the pressing member 124. In addition, a charging roller 126 that is a charging unit for charging the surface of the conveyance belt 121 is provided.

  Here, the conveyance belt 121 is an endless belt, and is stretched between the conveyance roller 127 and the tension roller 128, and the conveyance roller 127 rotates from the sub-scanning motor 131 via the timing belt 132 and the timing roller 133. By doing so, it is configured to go around in the belt conveyance direction (sub-scanning direction). A guide member 129 is disposed on the back side of the conveyance belt 121 in correspondence with the image forming area formed by the recording head 107.

  The charging roller 126 is arranged so as to contact the surface layer of the conveyor belt 121 and rotate following the rotation of the conveyor belt 121, and applies 2.5N to both ends of the shaft as a pressing force.

  Further, as a paper discharge unit for discharging the paper 112 recorded by the recording head 107, a separation unit for separating the paper 112 from the conveying belt 121, a paper discharge roller 152 and a paper discharge roller 153, and paper discharge A paper discharge tray 154 for stocking the paper 112 to be printed.

  A double-sided paper feeding unit 155 is detachably mounted on the back. The double-sided paper feeding unit 155 takes in the paper 112 returned by the reverse rotation of the transport belt 121, reverses it, and feeds it again between the counter roller 122 and the transport belt 121.

  Further, as shown in FIG. 10, a maintenance / recovery mechanism 156 for maintaining and recovering the state of the nozzles of the recording head 107 is arranged in the non-printing area on one side of the carriage 103 in the scanning direction.

  The maintenance / recovery mechanism 156 includes a cap 157 for capping each nozzle surface of the recording head 107, a wiper blade 158 which is a blade member for wiping the nozzle surface, and a discharge unit for discharging the thickened recording liquid. An empty discharge receiver 159 for receiving droplets when performing empty discharge for discharging droplets that do not contribute to recording is provided.

  In the image forming apparatus configured as described above, the sheets 112 are separated and fed one by one from the sheet feeding unit, and the sheet 112 fed substantially vertically upward is guided by the guide 115, and includes the conveyance belt 121 and the counter roller 122. The leading end is guided by the conveying guide 123 and pressed against the conveying belt 121 by the leading end pressing roller 125B, and the conveying direction is changed by about 90 °.

  At this time, a positive voltage output and a negative output are alternately repeated from the AC bias supply unit to the charging roller 126 by a control circuit (not shown), that is, a charging voltage pattern in which an alternating voltage is applied and the conveying belt 121 alternates. That is, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction which is the circumferential direction. When the paper 112 is fed onto the conveyance belt 121 charged alternately with plus and minus, the paper 112 is attracted to the conveyance belt 121 by electrostatic force, and the paper 112 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 121. Is done.

Therefore, by driving the recording head 107 according to the image signal while moving the carriage 103 in the forward and backward directions, ink droplets are ejected onto the stopped paper 112 to record one line, and the paper 112 is After transporting a predetermined amount, the next line is recorded.
(Recording on recording paper 112)
Upon receiving a signal that the trailing edge of the paper 112 has reached the recording area, the recording operation is terminated, and the paper 112 is discharged onto the paper discharge tray 154.

In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 112 is fed into the double-sided paper feeding unit 155 by rotating the conveyor belt 121 in the reverse direction. The paper 112 is reversed (with the back surface being the printing surface), and is fed again between the counter roller 122 and the conveyor belt 121. The timing is controlled, and the sheet is conveyed onto the conveyor bell 121 as described above. Then, after recording on the back surface, the paper is discharged to the paper discharge tray 154. Also, during printing (recording) standby, the carriage 103 is moved to the maintenance / recovery mechanism 156 side, and the nozzle surface of the recording head 107 is moved by the cap 157. Capping is performed to prevent ejection failure due to ink drying by keeping the nozzle in a wet state. In addition, the recording liquid is sucked from the nozzle while the recording head 107 is capped with the cap 157 (referred to as “nozzle suction” or “head suction”), and a recovery operation is performed to discharge the thickened recording liquid and bubbles. Wiping is performed by the wiper blade 158 in order to clean and remove ink adhering to the nozzle surface of the recording head 107 by the recovery operation. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 107 is maintained.

As described above, since the image forming apparatus includes the recording head constituted by the high-density liquid ejection head according to the present invention, it is possible to reduce the size and cost and to increase the number of ejectable nozzles with the same ejection head size. Therefore, further high-speed printing is possible. In the above-described embodiment, the present invention has been described with reference to an example in which the present invention is applied to an image forming apparatus having a printer configuration. However, the present invention is not limited to this, and may be applied to an image forming apparatus such as a printer / fax / copier multifunction machine. it can. Further, the present invention can be applied to an image forming apparatus using a recording liquid or a fixing processing liquid that is a liquid other than ink.
(Configuration of print operation start control of high-density liquid ejection head)
In the image forming apparatus of this embodiment, the initial temperature in the image forming apparatus (inside the apparatus) is determined by the environmental temperature (external temperature) of the place where the image forming apparatus is installed before driving. When a motor such as the scanning motor 104 or the sub-scanning motor 131 is driven, the internal temperature rises from the initial temperature due to heat generated by the motor. This in-machine temperature affects the printing performance of the high-density liquid discharge head.

  For this reason, in this embodiment, an in-machine temperature detecting element (main body temperature detecting element) 23 for detecting the atmospheric temperature in an image forming apparatus (in-machine) such as a printer is mounted in the carriage 103.

  In such an image forming apparatus, the liquid chamber 2 (individual liquid chamber 2) according to the first embodiment is performed by performing a preheating operation outside the printing area of the recording paper 112 by the high-density liquid ejection heads 107k, 107c, 107m, and 107y. ) Increase the ink temperature inside. In addition, when the temperature of the temperature detection element 22 in the high-density liquid ejection heads 107k, 107c, 107m, and 107y becomes equal to or higher than a predetermined value, the meniscus vibration can be increased to stably increase the idle ejection. It can be performed. The temperature in the liquid chamber 2 (individual liquid chamber) decreases due to exhaust heat due to the ink ejected in the idle state.

  A head temperature difference table with respect to the in-machine atmosphere temperature is held in a state slightly higher than the in-machine atmosphere temperature, and the printing operation can be started when the temperature difference falls within a predetermined range.

  This is because even in the normal printing state, the temperature rises by several degrees due to the balance between heat generation and exhaust heat.

  However, because the electrodes formed on the actuator substrate 1 of Example 1 and the actuator substrate 1 itself have high thermal conductivity, the high-density liquid ejection heads 107k, 107c, 107m, and 107y (hereinafter, simply abbreviated as the head in some cases). ) Temperature uniformity can be ensured.

  Here, head temperature data is obtained from a head temperature detection signal detected by a temperature detection element (abbreviated as a head temperature detection element in some cases) 22, and in-machine temperature data from an in-machine temperature detection signal from the in-machine atmosphere temperature detection element 23. Is obtained. The head temperature data and the in-machine temperature data are obtained as needed in real time and are input to the head controller (head controller) 24 shown in FIG. The head controller 24 controls the printing operation of the high-density liquid ejection heads 107k, 107c, 107m, and 107y. Further, a memory M is connected to the head controller 24, and temperature table data is stored in the memory M.

  As the temperature table data, for example, as shown in Table 1, it is data indicating the relationship between the in-machine atmospheric temperature at the start of driving of the image forming apparatus and the temperature difference at which the printing operation starts. When the in-machine atmosphere temperature at the start of driving of the image forming apparatus is high, the ink temperature in the first and second common liquid chambers 17a and 17b is high. Therefore, the higher the in-machine temperature, the smaller the temperature difference from the in-machine atmosphere. The data is set so that the printing operation is started.

  As a configuration of the main body sequence of such an image forming apparatus, the head controller 24 calculates the head temperature data, the in-machine temperature data, and the temperature table data obtained in real time, and determines to start the printing operation from the idle ejection operation. Etc.

  At this time, the head controller 24 detects the in-machine temperature data at the start of driving of the image forming apparatus by the in-machine atmosphere temperature detecting element 23 to obtain the in-machine atmosphere temperature in the initial driving of the image forming apparatus, and corresponds to the in-machine atmospheric temperature in the initial driving. Find the print start temperature difference. On the other hand, the head controller 24 calculates the actual temperature difference between the head temperature data obtained in real time and the in-machine temperature data.

  Then, the head controller 24 performs the preheating operation in step S1 in FIG. 12, performs idle ejection in step S2, and determines whether or not the head temperature has reached an appropriate temperature in step S3 based on the temperature table in Table 1. When it is determined that the head temperature has reached an appropriate temperature, that is, when the temperature difference corresponding to the in-machine temperature has reached the temperature difference (printing start temperature difference) described in the remarks of Table 1, the process proceeds to step S4 and the empty discharge operation is started. Make a decision to start the printing operation.

  The head controller (head control device) 24 is connected to the high-density liquid discharge heads 107k, 107c, 107m, and 107y via a flexible cable and a carriage 103 (not shown), and the high-density liquid discharge heads 107k, 107c. , 107m and 107y, the piezoelectric element 8 of the first embodiment is driven and controlled via the driving ICs (driving IC 15 of the first embodiment). Such a function of the head controller 24 can be provided to the driving IC 15.

  Regarding the temperature (head temperature) of the head section (high-density liquid ejection heads 107k, 107c, 107m, 107y) that starts printing after the idle ejection operation, the ink temperature in the common liquid chamber is high when the internal atmosphere temperature is high. The drive waveform voltage at the time of printing becomes low, and the heat generation at the piezoelectric element 8 and the driving IC 15 becomes low, so that the temperature increase width at the time of normal printing becomes small.

  For this reason, if the difference between the head temperature after empty ejection and the ambient temperature in the machine is large, the temperature will drop during printing, making it difficult to control the drive waveform. Set so that the printing operation starts when becomes smaller.

  Operation was confirmed in an ambient temperature of 10 ° C. with storage for one day.

  Ambient temperature: A preheating waveform is applied to all channels (nozzle 6 and liquid chamber 2) from 10 ° C., and the upper surface temperature of the nozzle plate 5 reaches 40 ° C. after about 10 seconds.

  Immediately after that, the empty discharge operation is performed.

A few seconds after the start of idle discharge, the upper surface temperature of the nozzle plate 5 is cooled to 13 ° C. or less, and by applying an actual drive waveform suitable for the upper surface temperature of the nozzle plate 5, normal discharge is performed in all channels (nozzles). It was confirmed.
(Supplementary explanation 1)
In a high-density liquid ejection head, it is desirable that the head configuration can be stably ejected even at a low temperature and in a meniscus dry state without complicating the head configuration, and then the printing operation is performed. Moreover, in order to reduce the maintenance frequency due to the ink suction operation or the like, it is desirable that the high-density liquid discharge head be refreshed by idle discharge so that normal discharge can be performed early.

  Therefore, the high-density liquid ejection head according to the embodiment of the present invention includes an actuator substrate 1 provided with a plurality of liquid chambers 2, a plurality of nozzles 6 that eject ink from the plurality of liquid chambers 2, and the liquid A thin-film diaphragm 7 that closes the upper portion of the chamber 2 and a thin-film piezoelectric element 8 provided on the diaphragm 7, and the diaphragm 7 is vibrated by the piezoelectric element 8. A thin-film actuator that pressurizes the ink in the liquid chamber 2, a driving IC 15 that is provided on the actuator substrate 1 and controls the driving of the piezoelectric element 8, and a head that detects the temperature in the liquid chamber 2. A temperature detection element (temperature detection element 22). The driving IC 15 controls the driving of the piezoelectric element 8 based on the detected temperature signal from the head temperature detecting element (temperature detecting element 22), so that the piezoelectric element 8 and the driving IC 15 are in the piezoelectric element 8. During the drive control, the ink temperature in the liquid chamber 2 can be raised by generating heat. In addition, the drive control applies a drive voltage waveform to the piezoelectric element 8 under the condition that ink is not ejected from the nozzle 6 before the start of printing, thereby causing the piezoelectric element 8 to generate heat and simultaneously generating heat. A preliminary heating step of the liquid chamber 2 for setting the ink temperature in the liquid chamber 2 to a predetermined temperature or more, and the ink in the liquid chamber 2 until the liquid (ink) in the liquid chamber 2 reaches an appropriate temperature for printing. An empty discharge step of discharging the nozzle from the nozzle, and a printing operation by discharging the liquid (ink) from the nozzle 6 when the liquid (ink) in the liquid chamber 2 reaches an appropriate temperature for printing. A printing process to be started.

  According to this configuration, in the high-density liquid ejection head, maintenance frequency due to ink suction operation or the like is reduced, so refreshing can be performed by idle ejection and normal ejection can be performed early.

  In addition, the piezoelectric element 8 that is a heating element and the driving IC 15 are mounted on the actuator substrate 1 to increase the ink temperature in the liquid chamber (individual liquid chamber) 2 in the ink non-ejection state, and suddenly due to exhaust heat during ink ejection. Therefore, in the maintenance operation during meniscus drying, the preheating process that does not discharge ink, the idle discharge process, and the printing operation is performed after the temperature drops due to idle discharge. A stable maintenance operation can be performed even in the head having the piezoelectric element 8.

The high-density liquid discharge head has a configuration in which the heat generation density of the high-density liquid discharge head is reduced and the heat capacity is reduced so that the high-density liquid discharge head can be heated.
(Supplementary explanation 2)
In addition, it is desirable that the high-density liquid ejection head can stably perform idle ejection even at a low temperature and in a meniscus dry state without complicating the head configuration, and then enters a printing operation.

  For this reason, in the high-density liquid ejection head according to the embodiment of the present invention, the driving IC 15 drives and controls the piezoelectric element 8 so that the ink temperature during the idle ejection is higher than the ink temperature during the printing operation. ing.

According to this configuration, meniscus vibration can be increased by performing idling while the preheating temperature is higher than the temperature during the printing operation, and the reliability of idling can be greatly improved. In addition, heat can be exhausted by idle ejection, and since the thermal capacity of the head is small, the temperature can be drastically lowered and the process can be shifted to a printing operation as it is.
(Supplementary explanation 3)
Further, in the high-density liquid discharge head, the current flowing through the wiring pattern on the actuator substrate 1 during preheating is suppressed, whereby the wiring film thickness on the actuator substrate 1 (first and second Com wirings 9 and 10, Vcom wiring 11). It is desirable to prevent electromigration without increasing the film pressure of 12).

  Therefore, the driving IC 15 of the high-density liquid ejection head according to the embodiment of the present invention drives and controls the piezoelectric element 8 so that the driving voltage waveform period of the piezoelectric element 8 is longer than the resonance period of the liquid chamber. It is supposed to let you.

According to this configuration, the drive voltage waveform cycle is longer than the resonance cycle of the liquid chamber (individual liquid chamber) 2 in the preheating step, so that the wiring portion on the actuator substrate 1 that flows during charging / discharging of the piezoelectric element 8 is performed. The maximum current and effective current of the (first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12) can be reduced, and the wiring thickness (first and second Com wirings) is used for reliability measures such as electromigration. 9, 10 and the film pressure of the Vcom wirings 11 and 12 are not required to be thickened, and the cost is not increased.
(Supplementary explanation 4)
Further, in the high-density liquid ejection head, the current flowing through the wiring pattern (first and second Com wirings 9 and 10 and Vcom wirings 11 and 12) on the actuator substrate 1 at the time of preheating is suppressed, so that the current on the actuator substrate 1 is reduced. It is desirable to prevent electromigration without increasing the wiring film thickness (film pressure of the first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12).

  For this reason, the driving IC 15 of the high-density liquid discharge head according to the embodiment of the present invention simultaneously preheats the heat generated by the piezoelectric element 8 by switching the target to be simultaneously driven and controlled among the plurality of piezoelectric elements 8. The number of the liquid chambers 2 is limited.

According to this configuration, in the preheating step, the number of channels (nozzles) to be preheated at the same time is limited, and the drive channel (liquid chamber 2) is switched and heated, whereby the actuator substrate that flows during charging and discharging of the piezoelectric element 8 1 can reduce the maximum current and effective current of the wiring portion (first and second Com wirings 9 and 10 and Vcom wirings 11 and 12), and can reduce the wiring thickness (first thickness) for reliability measures such as electromigration. It is not necessary to increase the film thickness of the first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12, and the cost is not increased.
(Supplementary explanation 5)
Further, in the high-density liquid ejection head, the current flowing through the wiring pattern (first and second Com wirings 9 and 10 and Vcom wirings 11 and 12) on the actuator substrate 1 at the time of preheating is suppressed, so that the current on the actuator substrate 1 is reduced. It is desirable that electromigration can be prevented without increasing the wiring film thickness (film pressure of the first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12).

  For this reason, the driving IC 15 of the high-density liquid ejection head according to the embodiment of the present invention has the pressure line element such that the period of the driving voltage waveform of the piezoelectric element 8 is shorter than the resonance period of the liquid chamber 2. 8 and the number of the liquid chambers 2 to be preheated simultaneously are limited by restricting the target of the piezoelectric element 8 that is simultaneously driven and controlled by the drive voltage waveform.

According to this configuration, in the preheating step, the drive voltage waveform period is shorter than the resonance period, and the number of channels (liquid chamber 2) to be preheated at the same time is limited and heated. The maximum current and effective current of the wiring portion (first and second Com wirings 9 and 10 and Vcom wirings 11 and 12) on the flowing actuator substrate 1 can be reduced, and the wiring film is used for reliability measures such as electromigration. It is not necessary to increase the thickness (film pressure of the first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12), and the cost is not increased.
(Supplementary explanation 6)
Further, in the high-density liquid ejection head, the current flowing through the wiring pattern (first and second Com wirings 9 and 10 and Vcom wirings 11 and 12) on the actuator substrate 1 at the time of preheating is suppressed, so that the current on the actuator substrate 1 is reduced. It is desirable that electromigration can be prevented without increasing the wiring film thickness (film pressure of the first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12).

  For this reason, the driving IC 15 of the high-density liquid ejection head according to the embodiment of the present invention controls the rise and fall times of the drive voltage waveform of the piezoelectric element 8 to be longer than the voltage waveform during ink ejection.

According to this configuration, in the preheating step, the rise and fall times of the drive voltage waveform are made longer than the voltage waveform at the time of ink ejection, whereby the wiring portion on the actuator substrate 1 that flows during charging / discharging of the piezoelectric element 8 ( The maximum current and effective current of the first and second Com wirings 9 and 10 and the Vcom wirings 11 and 12 can be reduced, and the wiring film thickness (first and second Com wirings 9 can be used for reliability measures such as electromigration. , 10, and the film pressure of the Vcom wirings 11 and 12 are not required to be thickened, and the cost is not increased.
(Supplementary explanation 7)
Further, in the high-density liquid ejection head, the power consumption in the vicinity of the ink supply port 16a during preliminary driving is increased, so that the cooling action by the ink in the first and second common liquid chambers 17a and 17b is compensated, and the head is made uniform. It is desirable to be able to preheat.

  For this reason, in the high-density liquid ejection head according to the embodiment of the present invention, the supply ports 16a for supplying ink to the common paths (first and second common liquid chambers 17a, 17b) communicating with the plurality of liquid chambers 2 are provided. 16b is provided so as to be close to a part of the plurality of liquid chambers 2, and the driving IC 15 is a spare for the piezoelectric element 8 corresponding to the liquid chamber 2 in the vicinity of the supply ports 16a and 16b. The power consumption by driving is made larger than the power consumption by preliminary driving of the piezoelectric elements 8 corresponding to the other liquid chambers 2.

According to this configuration, in the preheating process, the power consumption due to the preliminary driving of the channels (liquid chamber 2) in the vicinity of the supply ports 16a and 16b is made larger than that of the other channels (liquid chamber 2). In the vicinity of 16b, the temperature hardly rises due to heat radiation to the ink, but the temperature can be increased uniformly with respect to the nozzle rows (first and second nozzle rows Nz1, Nz2).
(Supplementary explanation 8)
Further, in the high density liquid discharge head, it is desirable that the meniscus vibration at the time of idle discharge is increased so that the maintenance operation can be reliably performed.

  For this reason, the driving IC 15 of the high-density liquid ejection head according to the embodiment of the present invention controls the drive voltage waveform in the idle ejection process to the resonance waveform of the liquid chamber 2.

According to this configuration, by applying a resonance waveform to the idle ejection waveform in the idle ejection waveform, the meniscus vibration can be increased and a stable idle ejection operation can be realized. Further, the driving voltage for idle ejection can be lowered, and the power consumption can be reduced.
(Supplementary explanation 9)
Further, in the high-density liquid ejection head, the current on the wiring pattern (first and second Com wirings 9 and 10 and Vcom wirings 11 and 12) on the actuator substrate 1 at the time of idle ejection is suppressed to suppress the current on the actuator substrate 1. It is desirable that electromigration can be prevented without increasing the wiring film thickness.

  For this reason, the driving IC 15 of the high-density liquid ejection head according to the embodiment of the present invention performs control for limiting the targets to be simultaneously driven and controlled among the plurality of piezoelectric elements 8 in the idle ejection process. The number of the liquid chambers 2 to be discharged simultaneously is limited, and the target to be driven and controlled simultaneously among the plurality of piezoelectric elements 8 is switched, thereby switching the target to be emptyly discharged among the plurality of liquid chambers 2. Like that.

In the idle ejection operation, the number of channels simultaneously idled is limited, and the channels (liquid chamber 2) are switched to perform idle ejection, whereby the wiring portion (first, first) on the actuator substrate 1 that flows when the piezoelectric element 8 is charged and discharged. The maximum current and effective current of the second Com wirings 9 and 10 and the Vcom wirings 11 and 12 can be reduced, and the wiring film thickness (first and second Com wirings 9 and 10, It is not necessary to increase the film thickness of the Vcom wirings 11 and 12, and the cost is not increased.
(Supplementary explanation 10)
In addition, in the high-density liquid discharge head, it is desirable that the distribution in the nozzle row at the time of preheating is made uniform and a stable maintenance operation can be secured.

  Therefore, in the high-density liquid ejection head according to the embodiment of the present invention, the driving IC 15 is mounted between at least two nozzle rows (first and second nozzle rows Nz1, Nz2).

According to this configuration, since the driving IC 15 is mounted between the two nozzle rows (first and second nozzle rows Nz1, Nz2), heat generated from the driving IC is generated by the nozzle rows (first and second nozzle rows). Nozzle rows Nz1, Nz2) can be transmitted uniformly, and the temperature can be increased uniformly during preheating, and the temperature can be decreased uniformly during idle ejection.
(Supplementary explanation 11)
It is also desirable to be able to provide an image forming apparatus that can ensure nozzle position accuracy at low cost.

  For this reason, in the high-density liquid discharge head according to the embodiment of the present invention, the head temperature at which the printing operation after empty discharge starts is higher than the in-machine atmosphere temperature, and the difference from the in-machine atmosphere temperature is compared with the temperature table. Judgment is made when the temperature falls below a predetermined temperature.

According to this configuration, the temperature at which the printing operation after the idle discharge is started is the time when the difference from the in-machine atmosphere temperature is equal to or lower than the predetermined temperature. This is because in consideration of the temperature rise after the start of printing, printing is started even when the ink temperature after idle ejection is higher than the atmosphere temperature inside the apparatus, so that the temperature change after the start of printing can be lowered.
(Supplementary explanation 12)
In the high-density liquid discharge head, the head temperature after the preliminary heating and the idle discharge operation is higher than the ambient temperature, but the head temperature fluctuation is suppressed to a predetermined value or less by the exhaust heat due to the ink during printing. Is desirable.

  For this reason, in the high-density liquid discharge head according to the embodiment of the present invention, the head temperature at which the printing operation after the idle discharge is started becomes smaller as the temperature difference from the in-machine atmosphere at the start of printing becomes higher. Is set to

According to this configuration, the temperature at which the printing operation after the idle discharge is started is made smaller as the temperature difference from the atmosphere inside the apparatus at the start of printing is higher. This is because the ink temperature increases with the ambient temperature in the machine, and the drive waveform voltage at the time of printing decreases, so that the temperature rise at the time of printing can be reduced, and the temperature change after the start of printing can be reduced. I have to.
(Supplementary explanation 13)
The higher the ambient temperature during preheating and idle ejection operation, the smaller the head temperature fluctuation due to exhaust heat due to ink during printing, so it is possible to shorten the time until printing starts after idle ejection ends. desirable.

  For this reason, the high-density liquid discharge head according to the embodiment of the present invention has a configuration in which the driving IC 15 is flip-chip mounted on the actuator substrate 1 and the back side of the driving IC 15 is not in contact with other members.

According to this configuration, the driving IC 15 is flip-chip mounted on the actuator substrate 1, and the back surface side of the driving IC 15 is not in contact with other members, so that heat is transferred from the driving IC 15 to the actuator substrate 1 side. The structure is easy to do. As a result, the temperature can be efficiently reduced in the preliminary heating process, and the temperature can be efficiently lowered by the exhaust heat from the ink in the idle ejection process.
(Supplementary explanation 14)
The image forming apparatus according to the embodiment of the present invention is equipped with the above-described high-density liquid ejection head.

  According to this configuration, it is possible to provide an image forming apparatus that can ensure a stable maintenance operation at low cost. In addition, a high-density, low-cost, high-density liquid discharge head using a thin-film piezoelectric element as an actuator is mounted, and a stable maintenance operation can be realized by empty discharge, thereby providing an image forming apparatus that can reduce the amount of waste ink.

DESCRIPTION OF SYMBOLS 1 Actuator board | substrate 2 Liquid chamber 3 Individual flow path 4 Individual communication path 5 Nozzle plate 6 Nozzle Nz1 1st nozzle row Nz2 2nd nozzle row 7 Vibration plate (thin film-like vibration plate)
8 Piezoelectric elements (thin film piezoelectric elements)
9 1st Com wiring (1st Com pattern wiring)
10 Second Com wiring (second Com pattern wiring)
11 Vcom wiring (Vcom pattern wiring)
12 Vcom wiring (Vcom pattern wiring)
15 Driving IC (control device)
16a supply port 16b supply port 17a first common liquid chamber 17b second common liquid chamber 18 FPC (flexible wiring board)
22 Temperature detection element 23 In-machine temperature detection element 24 Head controller

JP 2005-254463 A JP-A-11-138798

Claims (14)

An actuator substrate provided with a plurality of liquid chambers;
A plurality of nozzles for discharging ink from the plurality of liquid chambers;
A thin-film diaphragm that closes an upper portion of the liquid chamber; and a thin-film piezoelectric element provided on the diaphragm; and the diaphragm is vibrated by the piezoelectric element, whereby the liquid chamber A thin film actuator that pressurizes the ink of
A driving IC which is provided on the actuator substrate and controls driving of the piezoelectric element;
A head temperature detecting element for detecting the temperature in the liquid chamber,
The driving IC controls the driving of the piezoelectric element based on the detected temperature signal from the head temperature detecting element, so that the piezoelectric element and the driving IC generate heat during the driving control of the piezoelectric element, respectively. A high-density liquid ejection head capable of raising the ink temperature in a room,

The drive control applies a drive voltage waveform to the piezoelectric element under a condition in which ink is not ejected from the nozzle before printing starts, thereby causing the piezoelectric element to generate heat and simultaneously generating heat, thereby causing the ink temperature in the liquid chamber to Preheating step of the liquid chamber with a predetermined temperature or higher,
An empty discharge step of emptyly discharging ink in the liquid chamber from the nozzle until the liquid in the liquid chamber reaches an appropriate temperature for printing;
A printing step of starting a printing operation by discharging the liquid from the nozzle when the liquid in the liquid chamber reaches an appropriate temperature for printing;
A high-density liquid ejection head characterized by comprising:
2. The high-density liquid ejection head according to claim 1, wherein the driving IC drives and controls the piezoelectric element to make the ink temperature during the idle ejection higher than the ink temperature during the printing operation. High density liquid discharge head.
2. The high-density liquid ejection head according to claim 1, wherein the driving IC drives and controls the piezoelectric element so that a driving voltage waveform period of the piezoelectric element is longer than a resonance period of the liquid chamber. High density liquid discharge head.
2. The high-density liquid ejection head according to claim 1, wherein the driving IC switches the targets to be simultaneously driven and controlled among the plurality of piezoelectric elements, thereby simultaneously preheating the liquid chambers with the heat generated by the piezoelectric elements. A high-density liquid discharge head characterized by limiting the number.
2. The high-density liquid ejection head according to claim 1, wherein the driving IC drives and controls the piezoelectric element so that a period of the driving voltage waveform of the piezoelectric element is shorter than a resonance period of the liquid chamber, A high-density liquid ejection head, wherein the number of the liquid chambers to be preheated simultaneously is limited by limiting the target of the piezoelectric elements that are simultaneously driven and controlled by the driving voltage waveform.

  2. The high-density liquid ejection head according to claim 1, wherein the driving IC controls the rise and fall times of the drive voltage waveform of the piezoelectric element to be longer than the voltage waveform during ink ejection. Density liquid discharge head.   The high-density liquid ejection head according to claim 1, wherein a supply port for supplying ink to a common path communicating with the plurality of liquid chambers is provided so as to be close to a part of the plurality of liquid chambers, In the driving IC, power consumption due to preliminary driving of the piezoelectric element corresponding to the liquid chamber in the vicinity of the supply port is made larger than power consumption due to preliminary driving of the piezoelectric elements corresponding to other liquid chambers. A high-density liquid discharge head characterized by   2. The high-density liquid discharge head according to claim 1, wherein the driving IC controls the drive voltage waveform in the idle discharge step to a resonance waveform of the liquid chamber. 3.   2. The high-density liquid ejection head according to claim 1, wherein the driving IC performs control to limit targets to be simultaneously driven and controlled among the plurality of piezoelectric elements in the idle ejection step, and simultaneously performs the idle ejection. The high density is characterized in that the number of the liquid chambers is limited, and the target to be driven and controlled simultaneously among the plurality of piezoelectric elements is switched to switch the target to be discharged in the plurality of liquid chambers. Liquid discharge head.   2. The high density liquid discharge head according to claim 1, wherein the driving IC is mounted between at least two nozzle rows.   2. The high-density liquid discharge head according to claim 1, wherein the head temperature at which the printing operation after the idle discharge is started is higher than the in-machine atmosphere temperature, and a difference from the in-machine atmosphere temperature is equal to or lower than a predetermined temperature compared with the temperature table. A high-density liquid discharge head characterized by   2. The high-density liquid ejection head according to claim 1, wherein the head temperature at which the printing operation after the idle ejection is started is set to be smaller as the temperature difference from the in-machine atmosphere at the start of printing is higher. A high-density liquid discharge head characterized by comprising:   2. The high-density liquid discharge head according to claim 1, wherein the driving IC is flip-chip mounted on the actuator substrate, and the back side of the driving IC is not in contact with another member. Density liquid discharge head.   An image forming apparatus equipped with the high-density liquid discharge head according to claim 1.